1. Field of the Invention
This invention relates to a vehicle lamp having a plastic lens and more particularly to the surface formation of the lens.
2. Description of the Related Art
Transparent lenses or equivalents are now employed in vehicle lamps such as headlamps. However, such a lens becomes fogged with only a few waterdrops sticking onto its inner surface and this poses a problem in view of its external appearance as quality. Consequently, it has heretofore been contrived to adopt a lens whose inner surface is coated with an antifogging coating film.
In recent years, plastic lenses are increasingly adopted in vehicle lamps such as headlamps. This is because the plastic lenses are lightweight and excellent in shock resistance in comparison with glass lenses. However, the following problem will be posed when it is attempted to form an antifogging coating film on the inner surface of such a plastic lens.
More specifically, though a backing jig 6 for supporting a lens 4 is used as shown in FIG. 4 when an antifogging coating film 2 is formed, there develops a problem arising from the possibility that the backing jig 6 may come in contact with the outer surface 4a of the lens 4, thus scratching the lens 4.
An object of the present invention made in view of the aforementioned situation is to provide a vehicle lamp so that the outer surface of a lens may be prevented from being damaged when an antifogging coating film is formed on the outer surface thereof even in a case where a plastic lens with the antifogging coating film formed on the inner surface thereof is adopted.
The present invention is intended to the object above by arranging a lens so that a hard coating film is formed on the outer surface of the lens.
The present invention is characterized in that in a vehicle lamp having a plastic lens, wherein an antifogging coating film is formed on the inner surface of the lens; and a hard coating film is formed on the outer surface of the lens.
The range of forming the xe2x80x9cantifogging coating filmxe2x80x9d on the inner surface of the lens may cover the whole or part of the inner surface on condition that the range covers an area where a fogging problem is raised.
The range of forming a xe2x80x9chard coating filmxe2x80x9d on the outer surface of the lens may cover the whole or part of the outer surface on condition that the range covers an area where a scratching problem is raised.
As shown in the arrangement above, the vehicle lamp according to the present invention has adopted the plastic lens wherein the antifogging coating film is formed on the inner surface of the lens and the hard coating film is formed on the outer surface thereof. Consequently, the formation of the hard coating film before the formation of the antifogging coating film will prevent a backing jig from scratching the lens because of the hard coating film even though the backing jig is brought into contact with the outer surface of the lens when the antifogging coating film is formed.
Therefore, according to the present invention, the adoption of the plastic lens in the vehicle lamp with the antifogging coating film formed on the inner surface of the lens prevents the outer surface of the lens from being damaged when the antifogging coating film is formed.
As the antifogging coating film is formed on the inner surface of the lens in the vehicle lamp according to the present invention, even though the provision of a transparent lens or an equivalent can turn waterdrops sticking onto the inner surface of the lens into a water film because of the surface-active action of the antifogging coating film, whereby the deterioration of quality of the lens arising from making the lens look fogged can be prevented. On the other hand, the formation of the hard coating film on the outer surface of the lens contributes to improving the resistance of the outer surface to scratching, weather and solvent attack.
Although the xe2x80x9clensxe2x80x9d may be formed with or without lens elements on its inner surface, the arrangement proposed by the present invention is effective in the latter case because only a few waterdrops sticking onto the inner surface tends to make the lens look fogged.
Each of the lenses in vehicle lamps essentially consist of a lens front portion, a peripheral wall portion formed at the outer peripheral edge of the lens front portion, and a seal leg portion formed at the leading end of the peripheral wall portion, the seal leg portion being fitted and fixed to a lamp body, wherein therein it is desirous to form the antifogging coating film and the hard coating film on at least the lens front portion excluding the seal leg portion.
In other words, it is preferred that the antifogging coating film and the hard coating film should not be formed on the seal leg portion because the antifogging coating and hard coating films sticking onto the seal leg portion hardly smoothly have the lens fitted and fixed to the lamp body. On the other hand, it is preferred that the antifogging coating and hard coating films should be formed on the lens front portion so as not to make at least this portion become fogged and damaged because that portion can be seen from outside in such a state that the lamp has been mounted on the vehicle body.
With respect to the peripheral wall portion then, because it may be seen from the outside while the lamp is mounted on the vehicle body and it is preferred that the antifogging coating and hard coating films have been formed thereon in that case.
However, the lens front portion is formed of transparent lens and a relief is formed on the inner surface of the peripheral wall portion, whereupon the lens 12 will not become fogged even if some waterdrops stick to the inner surface of the peripheral wall portion. Further, the antifogging coating film may be formed in only the lens front portion, whereby the surface onto which the antifogging coating is applied becomes relatively simplified in shape and the antifogging coating area is decreased, which results in simplifying the work of applying the antifogging coating and also reducing the production cost.
By xe2x80x9cthe lens front portion formed of transparent coverxe2x80x9d in this case is meant that the lens front portion is completely made of transparent lens and also that part of the inner surface of the lens front portion is formed of lens elements.
Although it is preferred to form the antifogging coating film on the lens with its inner surface turned upward in view of workability of coating, even the application of the antifogging coating to the lens front portion may cause the coating to be stirred up the lens front portion because of the surrounding peripheral wall portion. If the peripheral wall portion is too high, the coating will stay in the inner space of the peripheral wall portion without escaping outside across the peripheral wall portion. As the antifogging coating contains surface-active agents and is hardly subjected to particle size reduction, the coating staying in the inner space of the peripheral wall portion falls onto the inner surface of the lens front portion and tends to deteriorate quality due to so-called seeding. In order to prevent the seeding, the height of the peripheral wall portion will have to be decreased to a certain extent so that the coating may easily escape outside across the peripheral wall portion. Therefore, the height of the inner surface of the peripheral wall portion is preferably set to 60 mm or less.
According to the present invention, an arrangement to fix the lens to the lamp body is not restrictive but may be made by using, for example, adhesives, sealing members with clips or weld bonding. The lens maybe securely fixed by weld bonding to the lamp body because the lens can be fixed to the lamp body even though the seal leg portion is relatively low with the effect of decreasing the total height of the peripheral wall portion and the seal leg portion. Thus, the deterioration of quality due to the seeding can be effectively prevented. The kind of xe2x80x9cweld bondingxe2x80x9d is not restrictive but inclusive of, for example, vibration fusion bonding such as ultrasonic fusion bonding, hot plate fusion bonding or the like.